What is the if in the map trying to do?
if $date eq $comp is false, map adds an undef to the returned list.
if $date eq $comp is true, map returns "$_\n".
Below, I assume that you're were trying to filter out dates that don't match. Filtering is grep's job, not map's. The "empty" elements you're getting are the undef returned by map when $date eq $comp is false.

$! doesn't have any meaningful value after calling -e.

The -e is redundant. opendir will fail if the dir doesn't exist, and you already handle that.

The capture in /^(\.+?)$/ wastes time. The ? is meaningless. I wonder if $_ eq '.' || $_ eq '..' would be faster.

It's probably faster to divide $comp in $year, $month, $day than to convert all the mtimes to strings.

sub list { 
   my ($path, $comp) = @_;

   $comp =~ m#^(..)/(..)/(....)$#
   or die("Error: Badly formatted \$comp.\n");

   my $comp_d = $1;
   my $comp_m = $2;
   my $comp_y = $3;

   local *DIR;
   opendir(DIR, $path)
   or die("Error: Unable to open directory $path: $!\n");

   my @filtered_listing;

   while (<DIR>) {
      next if /^\.+$/;

      my ($mtime_d, $mtime_m, $mtime_y) =
         (localtime( (stat "$path/$_")[9] ) )[3..5]; 

      next unless (
         $mtime_d == $comp_d &&
         $mtime_m == $comp_m &&
         $mtime_y == $comp_y
      );

      push(@filtered_listing, $_);
   }

   return sort @filtered_listing;
}

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In reply to Re^3: using grep on a directory to list files for a single date by ikegami
in thread using grep on a directory to list files for a single date by markkneen

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